1. Field of the Invention
The present invention relates to an interchangeable lens barrel having an image blur prevention system incorporated therein, and, more particularly, to an interchangeable lens barrel including an image blur prevention system having an image blur detection device to detect vibration, an image blur prevention optical system, and an image blur prevention optical system drive mechanism, which are arranged with respect to other lens barrel components in a manner which efficiently utilizes the space within the lens barrel.
2. Description of the Related Art
Interchangeable lens barrels are known which may be easily attached to and removed from a camera, such as a single-lens reflex camera. The known types of interchangeable lens barrels may include, for example, a zooming mechanism to adjust the focusing distance of a lens optical system from telephoto to wide-angle, and an autofocus (AF) mechanism to automatically perform subject focusing. Recently, image blur prevention systems have also been incorporated into lens barrels to compensate for camera vibration caused by, e.g., a photographer's hand movement, resulting in multiple functions incorporated into the lens barrel.
The types of lens barrels described above, having the image blur prevention system and the various other mechanisms, include a multiple lens optical system, multiple drives (including electric motors), control circuits, and sensors for sensing information related to the various mechanisms. The size of the lens barrel is determined by the diameter of the optical lens system contained inside the lens barrel. Since it is not desirable for the lens barrel to be made any larger than is necessary, the space inside the lens barrel must be used as effectively as possible. Therefore, the multiple drives, the control circuits, and the sensors must be arranged efficiently in the lens barrel.
However, the following problems occur in the known types of lens barrels which include an image blur prevention system. Specifically, the image blur prevention optical system is arranged to move within the lens barrel in a plane perpendicular to an optical axis I of a photographic optical system in the lens barrel. Accordingly, space must be preserved around the image blur prevention optical system so that the image blur prevention optical system can move. Recently, the drive motor that drives the image blur prevention optical system and the drive mechanics, such as a power transfer drive gear, have increased in size and complexity, requiring increased space for arranging these elements, and resulting in increased difficulty of assembly and disassembly due to the complexity. When the drive mechanics are arranged around the image blur prevention optical system, because of the space taken up by the drive mechanics the diameter of the optical system must be reduced.
Further, in general, the image blur prevention optical system drives are arranged with fixed parts connected to a fixed barrel, or with fixed parts connected to a fixed barrel portion that is connected to the lens barrel. With these kinds of lens barrels, it is desirable to reduce the lens barrel diameter as much as possible. However, when the diameter of the lens of an image blur prevention optical system is reduced, the amount of freedom for aberration adjustments is reduced and the blur adjustment tolerance also is reduced. Therefore, it is desirable to make the diameter of the image blur prevention lens as large as possible. To make the diameter of the image blur prevention lens as large as possible, the image blur prevention optical system drive must use the previously unused space within the lens barrel as efficiently as possible.
Furthermore, a focusing device, such as the AF mechanism, generally uses the drive power from the main body of the camera. Therefore, it is necessary to arrange the power transfer drive system for transferring power from the main body to the focusing device in a manner which efficiently utilizes the space inside the lens barrel.